This invention relates generally to dispensing devices and, particularly to repeating dispensers.
Repeating dispensers have been advantageously utilized in chromatographic work, but it is to be understood that the utility is not confined thereto. Repeating dispensers are utilized to provide, with one filling operation that sucks in a relatively large amount of fluid, repetitive, accurate discharges of exactly the same minute quantities of fluid.
U.S. Pat. No. 3,161,323 shows a repeating dispenser of the type aforementioned, and the construction thereof is simple; however, the dispenser has an index rod having rack teeth thereon and which is exposed to the outside, thus, it is difficult to handle the dispenser.
German patent disclosure No. P 2736551 discloses a generally tubular repeating dispenser having an actuating button on the top end. The dispenser is very easy to handle; however, there is a shortcoming that the relatively large amount of the liquid sucked and stored in the dispenser can only be dispensed by repeatedly depressing the actuating button, and that it is not easy to disassemble a cylinder and a piston from the dispenser which would be required in changing the liquid being sucked in and dispensed.
German patent disclosure No. 2926691 shows another repeating dispenser generally solving the problems aforementioned; however, there are many levers projecting sidewise from a generally tubular main body thus it is objectionable in the handling operation. piston device.
A repeating dispenser according to the invention comprises a tubular main body, an actuating member slidably disposed in the main body with the upper end thereof projecting out of the upper end of the main body and having a pressure button thereon, a spring for biasing upwards the actuating member, a spring retainer slidably disposed in the main body and normally abutting the lower end of the actuating member to transmit the biasing force of the spring to the actuating member, a stop provided on the inner surface of the main body for abutting engagement by the spring retainer in the non-actuated condition of the dispenser, a pawl pivotally connected to the spring retainer, a pawl spring for biasing the pawl in the radially outward direction, a rack shaft slidably provided on a side surface of the main body and having a plurality of rack teeth thereon for engaging with said pawl, means for preventing the pawl from engaging with the rack shaft when the spring retainer abuts against the stop, a suction button connected to the rack shaft and slidable along a longitudinal recess in the main body, and a cylinder piston device with the cylinder thereof being connected to the main body and the piston thereof being connected to the lower end of the rack shaft.
The rack teeth of the rack shaft do not engage with the pawl in the non-actuated condition, thus it is possible to refill or replenish the dispenser at any desired time and, further, the position of the suction button generally indicates the amount of fluid remaining in the cylinder piston device.
Preferably, the dispenser further comprises an adjusting member adjustably and rotatably mounted on the actuating member and having on the lower end thereof a plurality of circumferentially spaced steps for engaging with a second stop provided on the inner surface of the main body when the adjusting member moves downward in depressing the actuating member thereby adjusting the amount of fluid being dispensed in one actuation.